The goal of this research is the systematic investigation of the extent and source of individual differences in basic behavioral processes in perception and the relationship of these processes to measures of components of cognitive functioning. This includes: (a) the assessment of the nature and range of individual differences in perceptual processes, at the behavioral level; (b) the employment of signal detection methodology to separate the behavioral phenomena into their components of perceptual sensitivity and response criteria; (c) multivariate analysis of the derived variables aimed at a clearer understanding of the interrelationships among these behavioral phenomena; (d) genetic analysis of individual differences in both measures of perceptual sensitivity and decision parameters obtained from the signal detection approach; (e) a cross-sectional study of developmental patterns of these ariables in two independent populations; and (f) the relationship of the perceptual and criterion measures so obtained to measures of cognitive functioning, genetic markers, dermatoglyphic traits, and environmental variables.